The decisive change that has enabled us to see farther in 1972 than we could in 1929 is the advent of molecular biology.
Bernal recognized this in the 1968 foreword to his book, where he speaks of the double helix as “the greatest and most comprehensive idea in all science.”
We now understand the basic principles by which living cells organize and reproduce themselves.
Many mysteries remain, but it is inevitable that we shall understand the chemical processes of life in full detail, including the processes of development and differentiation of higher organisms, within the next century.
I consider it also inevitable and desirable that we shall learn to exploit these processes for our own purposes.
The next century will see a completely new technology growing out of the mastery of the principles of biology in the same way as our existing technology grew out of a mastery of the principles of physics.

The new biological technology may grow in three distinct directions.
Probably all three will be followed and will prove fruitful for particular purposes.
The first direction is the one that has been chiefly discussed by biologists who feel responsibility for the human consequences of their work; they call it “genetic surgery.”
The idea is that we shall be able to read the base-sequence of the DNA in a human sperm or egg-cell, run the sequence through a computer which will identify deleterious genes or mutations, and then by micromanipulation patch harmless genes into the sequence to replace the bad ones.
It might also be possible to add to the DNA genes conferring various characteristics to the resulting individual.
This technology will be difficult and dangerous, and its use will raise severe ethical problems.
Jacques Monod in his recent book Chance and Necessity sweeps all thought of it aside with his customary dogmatic certitude.
“There are,” he says, “occasional promises of remedies expected from the current advances in molecular genetics.
This illusion, spread by a few superficial minds, had better be disposed of.”
Although I have a great respect for Jacques Monod, I still dare to brave his scorn by stating my belief that genetic surgery has an important part to play in man's future.
But I share the prevailing view of biologists that we must be exceedingly careful in interfering with the human genetic material.
The interactions between the thousands of genes in a human cell are so exquisitely complicated that a computer program labeling genes “good” or “bad” will be adequate to deal only with the grossest sort of defect.
There are strong arguments for declaring a moratorium on genetic surgery for the next hundred years, or until we understand human genetics vastly better than we do now.

Leaving aside genetic surgery applied to humans, I foresee that the coming century will place in our hands two other forms of biological technology which are less dangerous but still revolutionary enough to transform the conditions of our existence.
I count these new technologies as powerful allies in the attack on Bernal's three enemies.
I give them the names “biological engineering” and “self-reproducing machinery.”
Biological engineering means the artificial synthesis of living organisms designed to fulfill human purposes.
Self-reproducing machinery means the imitation of the function and reproduction of a living organism with nonliving materials, a computer program imitating the function of DNA and a miniature factory imitating the functions of protein molecules.
After we have attained a complete understanding of the principles of organization and development of a simple multicellular organism, both of these avenues of technological exploitation should be open to us.